Intake engine valves

ABSTRACT

An intake engine valve may have a tapered portion positioned between a valve head and a valve stem tapering from a larger size to a smaller size in the direction of the valve stem. The valve stem may include a small diameter portion positioned between a guide stem portion And a stem end portion on the side of the tapered portion and having a diameter smaller than a diameter or diameters of the guide stem portion and the stem end portion. The guide stem portion may be guided by a valve guide of the engine.

This application claims priority to Japanese patent application serial number 2012-117368, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to intake engine valves.

JP-A-5-36009 teaches a known engine valve in which a valve stem has a small diameter portion having a diameter smaller than φd₂. The valve stem can be positioned in a number of locations ranging from on the surface of a valve head to a position spaced apart from the valve head surface. This distance is approximately φD/2 wherein φD is a diameter of the valve head and φd₂ is a diameter of the valve stem.

In the case of the known engine valve, the length of the small diameter portion is inevitably limited due to positioning within the range between the valve head surface and the position spaced from the valve head surface by the distance of approximately φD/2. Therefore, of the known engine is used as an intake engine valve, a problem may caused that the flow rate of intake air as well as the tumble flow may not be effectively increased. Simply increasing the length of the small diameter portion may lead to difficulty in ensuring the strength.

Therefore, there has been a need in the art for an intake engine valve that can increase the flow rate of intake air and the tumble flow, while the strength of the engine valve can be ensured.

SUMMARY OF THE INVENTION

In one aspect according to the present teachings, an intake engine valve may have a tapered portion positioned between a valve head and a valve stem and tapered toward the side of the valve stem. The valve stem may include a small diameter portion positioned between a guide stem portion and a stem end portion on the side of the tapered portion and having a diameter smaller than a diameter or diameters of the guide stem portion and the stem end portion. The guide stem portion may be guided by a valve guide of the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view, with a part omitted, of an intake engine valve according to a representative embodiment;

FIG. 2 is an enlarged front view of a portion around a valve head of the intake engine valve;

FIG. 3 is a sectional view of a portion of an engine around the engine valve showing the engine valve is an opened position;

FIG. 4 is a sectional view similar to FIG. 3 but showing the engine valve in a closed position;

FIG. 5 is a front view of a portion around a valve head of a comparative intake engine valve; and

FIG. 6 is a front view showing a portion around the valve head of the intake engine valve according to the representative embodiment and also showing a portion around the valve head of the comparative intake engine valve for comparison.

DETAILED DESCRIPTION OF THE INVENTION

Each of the additional features and teachings disclosed above and below may be utilized separately or in conjunction with other features and teachings to provide improved intake engine valves. Representative examples of the present invention, which examples utilize many of these additional features and teachings both separately and in conjunction with one another, will now be described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Moreover, various features of the representative examples and the dependent claims may be combined is ways that are not specifically enumerated in order to provide additional useful examples of the present teachings.

In one embodiment, a forged intake engine valve used for opening and closing an intake port of an engine may include a valve head, a valve stem and a tapered portion. The tapered portion may be positioned between the valve head and the valve stem and be tapered such that the tapered portion becomes smaller towards the side of the valve stem. The outer circumferential surface of the tapered portion may be formed as a tapered surface extending along a straight line as viewed in cross section with a taper angle. The valve stem may include a small diameter portion positioned between a guide stem portion and a stem end portion on the side of the tapered portion. The small diameter portion may have a diameter smaller than a diameter or diameters of the guide stem portion and the stem end portion. The guide stem portion may be guided by a valve guide of the engine.

With the provision of the small diameter portion and the tapered portion, it is possible to improve the mechanical strength of the engine valve. In this way, both the flow rate of intake air and the tumble flow may be increased by increasing the length of the small diameter portion while ensuring the mechanical strength of the engine valve.

The tapered surface and a backside surface of the valve head may be left as forged surfaces without being machined. Therefore, in comparison with the case where the entire circumferential surface of the engine valve is machined. It may be possible to reduce the number of process steps as well as reduce the manufacturing cost.

The small diameter portion may be formed such that a terminal end of the small diameter portion on the side of the stem guide portion is positioned proximal to an axial end of the valve guide on the side of the intake port when the engine valve is in an opened position. With this arrangement, it is possible to increase the flow rate of intake air and the tumble flow to or close to maximum values.

An intake engine valve according to a representative embodiment will now be described with reference to FIGS. 1 to 6. For the convenience of explanation, a peripheral device of the intake engine valve will be first described, and the intake engine valve will be described after that. FIG. 3 is a sectional view showing the peripheral device of the intake engine valve in the state where the engine intake valve is in an opened position. FIG. 4 is a sectional view similar to FIG. 3 but showing the intake engine valve in a closed position.

Referring to FIG. 3, a cylinder head 10 of an internal combustion engine may have an intake port 12 that communicates with a combustion chamber 11. A valve seat 13 may be disposed at a downstream end of the intake port 12. A metal valve guide 14 may be fitted into the cylinder head 10 so as to have the same axis as the valve seat 13. An intake engine valve 20 may have a valve head 22 and a valve stem 24. The intake engine valve 20 (more Specifically, the valve stem 24) may be supported within the valve guide 14 so as to be able to slidably move in an axial direction (vertical direction as viewed in FIG. 3), so that the valve head 22 can open and close the intake port 12 (more specifically, the valve seat 13). As the intake engine valve 20 is opened, the valve head 22 moves away from the valve seat 13, so that intake air can flow into the combustion chamber 11 via the intake port 12. However, as the intake engine valve 20 is closed (see FIG. 4), the valve head 22 moves such that it becomes seated on the valve seat 13, so that intake air is prevented from flowing into the combustion chamber 11 via the intake port 12.

The intake engine valve 20 will now be described. FIG. 1 shows a front view of the intake engine valve 20 with a part omitted. FIG. 2 shows a front view of a portion on the side of the valve head 22 of the intake engine valve 20.

Referring to FIG. 1, the intake engine valve 20 may be configured as a poppet valve and may be formed by a forging process. The valve head 22 and the valve stem 24 may have the same axis. An annular groove 25 may be formed in the outer circumferential surface of the terminal end portion (upper end portion as viewed in FIG. 1) throughout the circumferential length thereof. The annular groove 25 may serve as a mount groove, to which a retainer for a valve spring of a valve actuator (not shown) may be mounted. A large diameter-side surface (lower end surface as viewed in FIG. 1) of the valve head 22 may serve as a valve face 22 a facing the inside of the combustion chamber 11 (see FIG. 3). A shallow indent 23 may be formed towards the center of the valve face 22 a. As described previously, a forging process may be used to form the intake engine valve 20, which may include the valve head 22 and/or the valve stem 24. More specifically, the intake engine valve 20 may be forged from heat-resisting steel, titanium alloy, or any other suitable metal. As will be explained later, a machining operation such as an abrading or polishing operation may be performed on predetermined portions of the forged material.

As shown in FIG. 2, a tapered portion 26 may be formed at a transition position between the valve head 22 and the valve stem 24. The tapered portion 26 may be formed during a step in the forging operation. The tapered portion 26 is tapered toward the side of the valve stem 24 (upward). The outer circumferential surface of the tapered portion 26 may be formed as a tapered surface extending along a straight line as viewed from its cross-section within a plane that includes a longitudinal axis L of the engine valve 20. In the following explanation, the language “cross-section” is used to mean a cross-section within a plane that includes the longitudinal axis L of the engine valve 20, unless otherwise noted. The tapered portion 26 may have a taper angle θ1. For example, the taper angle θ1 may be 20°. The tapered portion 26 may have a minimum diameter 26 d that may conform to the diameter of the primary material before the forging process. A height H1 measured from the valve face 22 a to an axial end portion on the small diameter side of the tapered portion 26 may be 10 mm but may not be limited to this size.

In the following explanation, a portion of the valve stem 24 that is guided by the valve guide (see FIG. 3) will be referred to as a “guide stem portion 28”, and the end portion (lower end portion) of the valve stem 24 on the side of the tapered portion 26 will be referred to as a “stem end portion 29”. A small diameter portion 30 may be formed to be positioned between the guide stem portion 28 and the stem end portion 29. The small diameter portion 30 may have an outer diameter 30 d smaller than the outer diameters of both the guide stem portion 28 and the stem end portion 29. In one example, the outer diameter 30 d may be 4.5 mm but other sizes may be used. The remaining portion of the valve stem 24 may exclude the annular groove 23 and the smaller diameter portion 30 but include the guide stem portion 28 and the stem end portion 29. This remaining portion may have an outer diameter 24 d A height H2 measured from the valve face 22 a to a terminal end 30 a of the small diameter portion 30 on the side of the stem guide portion 28 may be 37 mm in one embodiment. Its size may be varied in other embodiments.

As shown in FIG. 3, the small diameter portion 30 may be formed such that the terminal end 30 a may be positioned on the side of the stem guide portion 28. Also, an axial end 14 a of the valve guide 14 may be positioned on the side of the intake port 12 (lower side as viewed in FIG. 3). When the engine valve 20 is in the open position, the terminal end 30 a may be positioned proximal to the axial end 14 a. As shown in FIG. 2, the end portion (upper end portion) of the small diameter portion 30 on the side of the guide stem portion 28 is configured as an upper connecting portion 31 a. The end portion (lower end portion) of the small diameter portion 30 on the side of the stem end portion 29 is configured as a lower connecting portion 31 b. The outer circumferential surfaces of the connecting portions 31 a and 31 b may be configured as curved surfaces smoothly continuing with the guide stem portion 28 and the stem end portion 29, respectively.

An annular surface 32 may be formed on the backside (i.e., the side opposite the valve face 22 a) of the valve head 22. The annular surface 32 may be a tapered surface extending along a straight line as seen in a cross-sectional view. It may be tapered from the outer circumferential end toward the backside (upwardly as viewed in FIG. 2) of the valve head 22 having a taper angle θ2. For example, the taper angle θ2 may be 45° in one embodiment but it may measure different angles in other embodiments.

The outer circumferential end of the valve head 22 may be configured as a circumferential end surface 34 having a relatively small axial length. The circumferential end surface 34 may have a cylindrical shape with the same diameter as the outer diameter of the large-diameter side edge of the annular surface 32. An inclined surface 36 configured as a conical surface may be also formed on the backside (i.e., the side opposite to the valve face 22 a) of the valve head 22. The inclined surface 36 may be configured as a tapered surface extending along a straight line as seen in a cross-sectional view. It may taper from the outer circumferential edge on the small-diameter side of the annular surface 32 toward the backside (upwardly as viewed in FIG. 2) of the valve head 22 by a taper angle θ3. The taper angle θ3 may be 12.5° to one embodiment but it may measure different angles in other embodiments.

A concave curved surface 38 may be also formed on the backside of the valve head 22 to connect between the large-diameter side outer circumferential edge of the tapered portion 26 and the small-diameter side outer circumferential edge of the inclined surface 36. The curved surface 38 may have a curvature radius R as seen in a cross-sectional view. In one example, the curvature radius R may be 7 mm. In this way, the inclined surface 36 and the curved surface 38 may constitute a backside surface of the valve head 22.

After the forging process, the annular surface 32, the circumferential end surface 34 and the valve stem 24 (including the guide stem portion 28, the stem end portion 29, the small diameter portion 30 and the annular groove 25) may be finished through a machining operation. Such a machining operation may, for example, be an abrasion or polishing operation. However, the tapered surface 26 and the backside surface (i.e., the inclined surface 36 and the curved surface 38) of the valve head 22 may be left as forged surfaces not having been machined. The height H1 may be measured from the valve face 22 a to the small-diameter side axial end portion of the tapered surface 26. This height may correspond to an end point (lower end point) of the valve stem 24 which may be machined. Therefore, the height H1 will be hereinafter also referred to as “a machined-end height H1”. The circumferential end surface 34 may optionally not be machined. An axial terminal end surface 24 a (upper end surface) of the valve stem 24 (see FIG. 1) may be machined or may not be machined.

With the intake engine valve 20 of the above embodiment, the tapered portion 26 is positioned between the valve head 22 and the valve stem 24. The valve head 22 and the valve stem 24 may be formed by a forging process. The intake engine valve 20 is preferably tapered from the side of the valve head 22 toward the side of the valve stem 24. The outer circumferential surface of the tapered portion 26 may be formed as a tapered surface extending along a straight line as seen from a cross-sectional view with a taper angle θ1. Therefore, it is possible to increase the mechanical strength of the engine valve 20. For this reason, it is possible to increase the axial length of the small diameter portion 30 of the valve stem 24 and to increase the flow rate of the intake air and the tumble flow. In this way, it is possible to increase the flow rate of the intake air and the tumble flow while ensuring the strength of the engine valve 20.

In addition, because the tapered surface 26 and the backside surface (i.e., the inclined surface 36 and the curved surface 38) of the valve head 22 are left as forged surfaces without being machined, it is possible to reduce the number of process steps in comparison with the case where the entire surface is machined after the forging operation. As a result, it is possible to reduce manufacturing costs.

Further, the small diameter portion 30 may be formed such that the terminal end 30 a on the side of the stem guide portion 28 may be positioned proximal to the axial end 14 a of the valve guide 14 on the side of the intake port 12 when the engine valve 20 is in the opened position. Therefore, it is possible to increase the flow rate of the intake air and the tumble flow to maximum or close to maximum values. In some arrangements, however, the terminal end 30 a is positioned within the length of the valve guide 14 when the engine valve 20 is in the opened position. This may result in a reduction in the length of the valve guide 14 which supports the stem guide portion 28. In the embodiment described above, where the terminal end 30 a is positioned proximal to the axial end 14 a, such a reduction in length of the valve guide 14 can be avoided.

Next, the engine valve 20 of the above embodiment will be described further in comparison to a comparative example shown in FIG. 5. FIG. 5 shows a front view of a valve head 122 of an intake engine valve 120 according to the comparative example (hereinafter referred to as “comparative engine valve 120”). FIG. 6 is a view, in which a front view of the valve head 22 is indicated by solid lines, while a front view of the portion around the valve head 122 of the comparative engine valve 120 is indicated by dotted lines. In FIGS. 5 and 6, like members are given the same reference numerals as the above embodiment and the description of these members will not be repeated.

Referring to FIG. 5, a comparative engine valve 120 has a valve head 122 and a valve stem 124. However, the comparative engine valve 120 does not include the tapered portion 26 (see FIG. 2) as in the above embodiment. In addition, the valve stem 124 does not have the small diameter portion 30 (see FIG. 2) as in the above embodiment. The valve stem 124 has an outer diameter 124 d that is the same as the outer diameter 24 d of the valve stem 24 of the above embodiment. A height h1 corresponds to an end point (lower end point) on the side of the valve head 122 of a machined region of the valve stem 124 and may be referred to as “a machined-end height h1”. The machined-end height h1 is set to 14 mm. Because the machined-end height H1 of the above embodiment may be set to 10 mm, the machined-end height H1 is smaller than the machined-end height h1.

Similar to the above embodiment, the valve head 122 has the annular face 32 and the circumferential end surface 34. A chamfered conical surface 137 is formed on the backside of the valve head 122. A chamfered angle θ4 of the conical surface 137 may be set, for example, to 30°. A concave curved surface 138 is preferably formed on the backside of the valve head 122 to connect the valve stem 124 and the chamfered conical surface 137. The curved surface 138 may have a radius r. In this way, the engine valve 20 of the above embodiment does not have a chamfered conical surface 137, and the radius R of the concave curved surface 38 may be smaller than the radius r of the comparative example. For this reason, the valve head 22 of the above embodiment may have a smaller thickness in the axial direction than that of the valve head 122 of the comparative engine valve 120 (see FIG. 6). In addition, a machining operation, such as an abrasion or polishing operation is performed on the entire outer circumferential surface of the comparative engine valve 120.

The engine valve 20 of the above embodiment is different from the comparative engine valve 120 in that the valve stem 24 has the tapered surface 26, so that the mechanical strength can be improved. In this way, it is possible to increase the axial length of the small diameter portion 30 of the valve stem 24, thereby leading to an increase in the flow rate of intake air and to an increase of the tumbling flow. In addition, in the engine valve 20 of the above embodiment, the tapered surface 26 and the backside surface (i.e., the inclined surface 36 and the curved surface 38) of the valve head 22 may be left as forged surfaces without being machined. Therefore, in comparison with the comparative engine valve 120 that requires the machining operation of the entire outer circumferential surface, it is possible to reduce the number of process steps and to reduce manufacturing costs. It was previously mentioned that the thickness in the axial direction of the valve head 22 may be smaller than that of the valve head 122 of the comparative example. Similarly, the machined-end height H1 may be smaller than the machined-end height h1. It is possible to increase the axial length of the small diameter portion 30 of the valve stem 24, so that the flow rate of intake air and the tumbling flow can be further increased. The weight of the engine valve 20 may be smaller than that of the comparative engine valve 120. 

What is claimed is:
 1. A forged intake engine valve used for opening and closing an intake port of an engine, comprising: a valve head; a valve stem; and a tapered portion positioned between the valve head and the valve stem and having a tapered surface tapering from the valve head towards the valve stem, the tapered surface extending along a straight line as viewed in its cross-section and having a taper angle; and wherein the valve stem includes a small diameter portion positioned between a guide stem portion and a stem end portion on a side of the tapered portion and having a diameter smaller than both a diameter of the guide stem portion and a diameter of the stem end portion, the guide stem portion being configured to be guided by a valve guide of the engine.
 2. The forged intake engine valve according to claim 1, wherein the tapered surface and a backside surface of the valve head are left as forged surfaces without being machined.
 3. The forged intake engine valve according to claim 1, wherein the small diameter portion is formed such that a terminal end of the small diameter portion on the side of the stem guide portion is positioned proximal to an axial end of the valve guide on the side of the intake port when the engine valve is in an opened position.
 4. The forged intake engine valve according to claim 2, wherein the small diameter portion is formed such that a terminal end of the small diameter portion on the side of the stem guide portion is positioned proximal to an axial end of the valve guide on the side of the intake port when the engine valve is in an opened position.
 5. The forged intake engine valve according to claim 1, wherein the taper angle of the tapered portion is about 20°.
 6. The forged intake engine valve according to claim 1, wherein the small diameter portion includes opposite end portions with curved outer surfaces respectively smoothly connected to outer surfaces of the guide stem portion and the stem end portion.
 7. The forged intake engine valve according to claim 2, wherein: the backside surface of the valve head has a concave surface positioned on the side of the small diameter portion and an inclined surface positioned on the side opposite the small diameter portion; the concave surface has a radius; and the inclined surface is configured as a tapered surface extending along a straight line and tapering toward the concave surface.
 8. An intake engine valve need for opening and closing an intake port of an engine, comprising: a valve head; a valve stem; and a tapered portion positioned between the valve head and the valve stem and tapering towards the valve stem, an outer circumferential surface of the tapered portion being formed as a tapered surface extending along a straight line in a cross-sectional view and also having a taper angle; and wherein the valve stem includes a small diameter portion positioned between a guide stem portion and a stem end portion on the side of the tapered portion and having a diameter smaller than both a diameter of the guide stem portion and a diameter of the stem end portion, the guide stem portion being configured to be guided by a valve guide of the engine. 